Image forming apparatus, system on chip unit and driving method thereof

ABSTRACT

An image forming apparatus which is connected to a host apparatus, the image forming apparatus including a first memory, a second memory, a universal serial bus (USB) interface to receive a USB control signal or a USB data signal from the host apparatus, and a central processing unit (CPU) operating in a normal mode using the first memory or a power saving mode using the second memory. If the USB data signal is input in the power saving mode, the CPU activates the first memory and converts the power saving mode into the normal mode, and, if the USB control signal is input in the power saving mode, the CPU retains the power saving mode and performs an operation corresponding to the USB control signal using the second memory. Accordingly, the power saving mode is realized effectively.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No.10-2009-0084921, filed on Sep. 9, 2009, and No. 10-2010-0058266, filedon Jun. 18, 2010, in the Korean Intellectual Property Office, thedisclosures of which are incorporated herein by reference.

BACKGROUND

1. Field

Aspects relate to an image forming apparatus, a system on chip (SoC)unit, and a driving method thereof, and more particularly, to an imageforming apparatus and a SoC unit which have a universal serial bus (USB)communication function, and a driving method thereof.

2. Description of the Related Art

A power saving mode refers to a mode in which power supplied to most ofthe modules is interrupted or minimized in order to minimize powerconsumption when a system is idle. In order to reduce standby power, amethod of interrupting power supplied to a main memory (an externaldynamic random access memory (DRAM) in general) or getting a system in aself refresh state and then driving a program in an unused internalmemory of a SoC (an internal static random access memory (SRAM) ingeneral) may be used. In general, the SRAM uses a low capacity memory ofabout 128 KB.

However, if it is necessary to transmit a great amount of data as in aUSB driver for a printer or a mass storage device or if the number ofsupported interfaces increases, a space occupied by stack increases andthus it is difficult to perform all functions of the USB driver in thelow capacity SRAM.

Also, since the SRAM is expensive, a high capacity SRAM is ineffectivein view of a cost.

If an apparatus used as a USB device interrupts power supplied to theexternal DRAM in order to enter the power saving mode, the USB driveroperating in the external DRAM is also stopped so that the USB devicedoes not communicate with a host device. In particular, in the case of aprinter which receives a specific command from a host apparatus througha USB, the printer is not able to perform its original function (aproblem that a personal computer recognizes the printer as beingdisconnected). Therefore, in the related art, the external DRAM isnormally operated even in the power saving mode.

However, if power continues to be supplied to the external DRAM, standbypower is consumed. On the other hand, if power supplied to the DRAM isinterrupted in order to reduce power consumption, the USB driveroperating in response to the external DRAM is also stopped so thatcommunication using the USB is impossible. However, in this case, if aprogram for checking an apparatus status using the USB gets access tothe apparatus, it determines that power is turned off and thus there isan inconvenience in using a service. For example, if a personal computeris connected to a printer through a USB and a print monitoring programis installed in the PC, there is a problem that the PC may recognize theprinter as being in an abnormal state or being disconnected when theDRAM of the printer is turned off and the USB driver does not operate.

SUMMARY

Accordingly, it is an aspect to provide an image forming apparatus whichrealizes a power saving mode effectively and a driving method thereof.

Additional aspects and/or advantages will be set forth in part in thedescription which follows and, in part, will be apparent from thedescription, or may be learned by practice of the invention.

The foregoing and/or other aspects are achieved by providing an imageforming apparatus which is connected to a host apparatus, including: afirst memory, a second memory, a universal serial bus (USB) interface toreceive a USB control signal or a USB data signal from the hostapparatus, and a central processing unit (CPU) operating in a normalmode using the first memory or in a power saving mode using the secondmemory, wherein, if the USB data signal is input in the power savingmode, the CPU activates the first memory and converts the power savingmode into the normal mode, and, if the USB control signal is input inthe power saving mode, the CPU retains the power saving mode andperforms an operation corresponding to the USB control signal using thesecond memory.

The USB data signal may be a request signal for an image forming job.

The CPU may interrupt power supplied to the first memory or retain thefirst memory in a self-refresh state in the power saving mode.

The second memory and the CPU may be provided inside a system on chip(SoC), and the USB interface may be provided inside or outside the SoC.

If the image forming apparatus enters the power saving mode, the CPU maycopy a program for controlling the power saving mode from the firstmemory to the second memory.

The program for controlling the power saving mode may include at leastone of a routine for determining whether a signal is input to the USBinterface or not, a routine for performing an operation according to theUSB control signal, and a routine required in a wake up process forconverting the power saving mode into the normal mode.

The USB control signal may be input through a control endpoint, and theUSB data signal may be input through a bulk type in/out endpoint.

The foregoing and/or other aspects may also be achieved by providing animage forming apparatus which is connected to a host apparatus,including: a first memory, a second memory, a USB interface to receive aUSB control signal or a USB data signal from the host apparatus, a firstCPU to perform an operation using the first memory in a normal mode andbeing deactivated if the normal mode is converted into a power savingmode, and a second CPU to perform an operation using the second memoryin the power saving mode, wherein, if the USB data signal is input inthe power saving mode, the second CPU activates the first CPU to convertthe power saving mode into the normal mode, and if the USB controlsignal is input in the power saving mode, the second CPU retains thepower saving mode and performs an operation corresponding to the USBcontrol signal using the second memory.

The USB data signal may be a request signal for an image forming job.

The second CPU may interrupt power supplied to the first CPU or retainthe first memory in a self-refresh state in the power saving mode.

The foregoing and/or other aspects may also be achieved by providing aSoC unit which is mountable on an apparatus having a volatile memory,the SoC unit including: a memory, a USB interface to receive a USBcontrol signal or a USB data signal from an external apparatus connectedto the apparatus, and a CPU to perform an operation using the volatilememory in a normal mode and perform an operation using the memory in apower saving mode, wherein, if the USB data signal is input in the powersaving mode, the CPU converts the power saving mode into the normal modeand performs an operation corresponding to the USB data signal, and ifthe USB control signal is input in the power saving mode, the CPUretains the power saving mode and performs an operation corresponding tothe USB control signal using the memory.

The foregoing and/or other aspects may also be achieved by providing adriving method of an image forming apparatus which is connected to ahost apparatus, includes a first memory, a second memory, and a USBinterface to receive a USB control signal or a USB data signal from thehost apparatus, and operates in a normal mode using the first memory orin a power saving mode using the second memory, the driving methodincluding: detecting a signal that is input from the host apparatus inthe power saving mode, and if the input signal is the USB controlsignal, retaining the power saving mode and performing an operationcorresponding to the USB control signal using the second memory, and ifthe input signal is the USB data signal, converting the power savingmode into the normal mode to activate the first memory and performing anoperation corresponding to the USB data signal using the activated firstmemory.

The USB data signal may be a request signal for an image forming job.

In the power saving mode, power supplied to the first memory may beinterrupted or the first memory may be retained in a self-refresh state.

The driving method may further include, if the image forming apparatusenters the power saving mode, copying a program stored in the firstmemory for controlling the power saving mode to the second memory.

The program for controlling the power saving mode includes at least oneof a routine for determining whether a signal is input to the USBinterface or not, a routine for performing an operation corresponding tothe USB control signal, and a routine required in a wake-up process forconverting the power saving mode into the normal mode.

The USB control signal may be input through a control end point and theUSB data signal may be input through a bulk type in/out endpoint.

The foregoing and/or other aspects may also be achieved by providing adriving method of an image forming apparatus which is connected to ahost apparatus, includes a first memory, a second memory, a first CPU toperform an operation using the first memory in a normal mode and beingdeactivated if the normal mode is converted into a power saving mode,and a second CPU to perform an operation using the second memory in thepower saving mode, the driving method including: detecting a signal thatis input from the host apparatus in the power saving mode, and if theinput signal is the USB control signal, retaining the power saving modeand performing an operation corresponding to the USB control signalusing the second memory, and if the input signal is the USB data signal,activating the first CPU and converting the power saving mode into thenormal mode.

The USB data signal may be a request signal for an image forming job.

In the power saving mode, power supplied to the first CPU may beinterrupted or the first memory may be retained in a self-refresh state.

The foregoing and/or other aspects may also be achieved by providing adriving method of a SoC unit which is mountable on an apparatus having avolatile memory accessible in a normal mode, and includes a USBinterface to receive a USB control signal or a USB data signal from anexternal apparatus connected to the apparatus, and a memory, the drivingmethod including: detecting a signal that is input from the apparatus inthe power saving mode; and if the input signal is the USB data signal,converting the power saving mode into the normal mode, and if the inputsignal is the USB control signal, retaining the power saving mode andperforming an operation corresponding to the USB control signal usingthe memory.

The foregoing and/or other aspects may also be achieved by providing astorage medium in which a program code for executing a driving method ofan image forming apparatus is stored, the image forming apparatus beingconnected to a host apparatus, including a first memory, a secondmemory, and a USB interface to receive a USB control signal or a USBdata signal from the host apparatus, and operating in a normal modeusing the first memory or in a power saving mode using the secondmemory, the driving method including: detecting a signal that is inputfrom the host apparatus in the power saving mode, and if the inputsignal is the USB control signal, retaining the power saving mode andperforming an operation corresponding to the USB control signal usingthe second memory, and if the input signal is the USB data signal,converting the power saving mode into the normal mode and performing anoperation corresponding to the USB data signal.

Accordingly, the power saving mode is realized effectively.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages will become apparent and morereadily appreciated from the following description of the embodiments,taken in conjunction with the accompanying drawings of which:

FIG. 1A is a block diagram illustrating an image forming apparatusaccording to an exemplary embodiment;

FIG. 1B is a block diagram illustrating an image forming apparatusaccording to another exemplary embodiment;

FIGS. 2A to 2C are views illustrating diverse examples of the imageforming apparatus of FIG. 1A;

FIGS. 3A to 4 are block diagrams to explain a relationship between theimage forming apparatus of FIG. 1A and a host apparatus;

FIG. 5 is a view illustrating a USB packet analysis frame according toan exemplary embodiment;

FIG. 6 is a flowchart illustrating a driving method of an image formingapparatus according to an exemplary embodiment; and

FIG. 7 is a flowchart illustrating a driving method of an image formingapparatus according to another exemplary embodiment.

DETAILED DESCRIPTION

Reference will now be made in detail to the present embodiments,examples of which are illustrated in the accompanying drawings, whereinlike reference numerals refer to the like elements throughout. Theembodiments are described below in order to explain the embodiments byreferring to the figures.

FIG. 1A is a block diagram illustrating an image forming apparatusaccording to an exemplary embodiment.

Referring to FIG. 1A, an image forming apparatus 100 includes auniversal serial bus (USB) interface 110, a central processing unit(CPU) 120, a first memory 130, a second memory 140, a power supply unit150, a function unit 160, and an operation module 170.

The image forming apparatus 100 may be realized as a printer, a copier,a scanner, a facsimile machine, or a multifunction peripheral (MFP)combining the functions of the aforementioned devices in a singledevice.

The USB interface 110 functions to USB communicate with at least oneexternal apparatus. The at least external apparatus may be a hostapparatus such as a personal computer (PC).

More specifically, the USB interface 110 may perform USB controlcommunication and USB data communication with the at least one externalapparatus. That is, the USB interface 110 may receive a USB controlsignal and a USB data signal from the at least one external apparatus.The USB interface 110 may be an endpoint which is a logic point definedin the USB specification and a detailed description thereof will begiven below.

The CPU 120 controls the overall operation of the image formingapparatus 100, and more particularly, may operate in a normal mode inwhich the first memory 130 is used or a power saving mode in which thesecond memory 140 is used.

More specifically, the CPU 120 converts the power saving mode into thenormal mode when the USB data signal is input, thereby activating thefirst memory 130 and performing an operation corresponding to the USBdata signal using the activated first memory 130. The USB data signalrecited herein may be a request signal regarding an image forming job.

Also, when the USB control signal is input in the power saving mode, theCPU 120 retains the power saving mode and performs an operationcorresponding to the USB control signal using the second memory 140. TheUSB control signal recited herein may be a status request signal of theimage forming apparatus generated by an application provided in a hostapparatus (not shown). For example, an apparatus comprising theapplication may be realized by a smart panel provided in the hostapparatus. The smart panel is a panel that displays a status of theimage forming apparatus through the host apparatus, and for example, thesmart panel may periodically recognize the status of the image formingapparatus through the USB control communication. A user may knowprinting status, paper status, toner status, power on/off status of theimage forming apparatus displayed on the host apparatus by the smartpanel.

In addition, when the USB control signal is input in the power savingmode, the CPU 120 retains the power saving mode and performs anoperation corresponding to the USB control signal using the secondmemory 140.

That is, if there is a request for status information of the imageforming apparatus 100 in the smart panel when the image formingapparatus 100 is in the power saving mode, the CPU 120 may recognizewhether the image forming apparatus 100 is in the power saving mode ornot through the USB control communication.

The normal mode recited herein refers to a mode in which the imageforming apparatus 100 performs a normal operation, and the power savingmode refers to a mode in which power supplied to the most of modules isinterrupted or minimized in order to minimize power consumption when asystem is idle. In order to reduce standby power in the power savingmode, power supplied to a main memory (external DRAM in general) isinterrupted or a program in an unused internal memory (internal SRMA ingeneral) of a SoC is driven after entering a self-refresh mode. Forexample, the SRAM may use a low capacity memory of about 128 KB.However, in some situations, a synchronous dynamic RAM (SDRAM) may beused and a read-only memory (ROM) may be additionally used along withthe SRAM or the SDRAM.

The first memory 130 is a main memory used in the normal mode and may berealized as a non-volatile memory. For example, the first memory 130 maybe a dynamic RAM (DRAM). The first memory 130 stores a program or anapplication that can support the USB communication in the normal mode,such as a USB driver.

The second memory 140 may be used in the power saving mode whichrequires less power than the normal mode. For example, a program forcontrolling the power saving mode may include at least one of a routinefor determining whether a signal is input into the USB interface 110 ornot, a routine for performing an operation corresponding to the USBcontrol signal, and a routine required in a wake-up process forconverting into the normal mode.

The second memory 140 stores a program or an application for supportingthe power saving mode and may be realized as at lease one of a staticRAM (SRAM) or a synchronous dynamic random access memory (SDRAM). Besidethese, RAMBus, DRAM, double data rate (DDR)-SDRAM may be used.

Also, at least one of a read only memory (ROM) and a flash memory may beused to store a code necessary in the normal mode.

According to an exemplary embodiment, the second memory 140 may berealized as an SRAM. In this case, the SRAM may be used in copying andexecuting a code necessary in the normal mode and stored in the DRAM,ROM or flash memory.

The second memory 140 may be realized as an SRAM and may be used toexecute a code stored in the ROM or the flash memory and necessary inthe power saving mode.

Also, the second memory 140 may be realized as an SDRAM and may be usedto execute a code stored in the ROM or the flash memory and necessary inthe power saving mode.

Also, the second memory 140 may be used along with the first memory 130in the normal mode. That is, the SRAM used as a buffer when an image isprocessed in the normal mode is reutilized as the second memory 140 inthe power saving mode.

In the power saving mode, the CPU 120 may interrupt the power suppliedto the first memory 130, reduce an operation frequency of the firstmemory 130, or control the first memory 130 to be retained in aself-refresh state.

Hereinafter, each memory will be described briefly for easyunderstanding of the present disclosure.

The SRAM maintains its data while power is being supplied to the memory.The SRAM does not require periodic multiple re-writing operations andthus maintains its data by writing it once. The SRMA is a low capacitymemory and has a high operation speed, but has a drawback that it isexpensive compared to the DRAM. Therefore, the SRAM is used in a memorywhich requires a high speed but does not require a high capacity such asa cache memory.

The DRAM should re-write data continuously in order to maintain its dataunlike the SRAM. The DRAM is a mass storage memory and is slower thanthe SRAM. The DRAM is used as a main memory for most of systems.

The SDRAM operates keeping pace with a system clock. Since the SDRAMkeeps pace with a system bus speed up to 200 MHz theoretically andoperates depending on the system clock, a high system speed may beachieved.

The power supply unit 150 supplies power to the image forming apparatus100.

Although the CPU 120 controls the image forming apparatus 100 in theabove exemplary embodiment, in some situation, the CPU 120 may transmita command to a controller (not shown) such that each element performsits corresponding operation.

Also, the image forming apparatus 100 may include a phase-locked loop(PLL) unit (not shown) to generate different operation frequencies. ThePLL unit (not shown) may provide the generated operation frequencies tothe CPU 120 and the first memory 130.

The function unit 160 performs diverse functions such as processing animage, and compressing or decompressing the image in order for an engineunit (not shown) to perform an image forming job such as printing,copying, and scanning.

The operation module 170 may include diverse function modules that arenot included in the function unit 160 due to the limited capacity of thefunction unit 160. The operation module 170 may include at least onefunction module, and the at least one function module may be realized asa single chip.

The CPU 120 may convert the normal mode into the power saving mode if apredetermined condition is satisfied. For example, there may be nocommand during a predetermined time. However, this is merely an example.There are diverse situations as a mode conversion event.

Also, the CPU 120 is converted from the power saving mode into thenormal mode if a predetermined condition is satisfied. For example, inthe case of a printer, if there is an event such as panel key input,printing service request, or fax ring, the CPU 120 is converted from thepower saving mode into the normal mode.

When the CPU 120 is required to be converted from the normal mode intothe power saving mode as described above, the CPU 120 may copy a programfor controlling the power saving mode from the first memory 130 to anexecutable area of the second memory 140, or may copy a program storedin an extra ROM or flash memory to an executable area of the secondmemory 140. The program for controlling the power saving mode includes aUSB driver, and the USB driver may include only a routine to recognizean interrupt from a control endpoint or a data endpoint, a routineresponsible for processing a control endpoint, and a routine required ina wake-up process to return to the normal mode. Accordingly, the programfor controlling the power saving mode has less capacity than a USBprogram stored in the first memory 130 used in the normal mode.

If a code has been completely copied, the power supplied to the entiresystem modules including the first memory 130 is interrupted and theimage forming apparatus 100 enters the power saving mode.

The code may be copied from the flash memory or the ROM to the DRAM whenthe image forming apparatus 100 is booted or may be copied to the SRAMwhen the image forming apparatus 100 enters the power saving mode.

In the power saving mode, the CPU 120 checks whether there is aninterrupt from the USB interface 110.

If there is the interrupt from the USB interface 110, the CPU 120determines whether the interrupt is from the control endpoint or thedata endpoint.

If the interrupt is not from the control endpoint, for example, if theinterrupt is from the data endpoint (for example, if there is a requestfor an image forming job), the CPU 120 read outs printer data and storesit in the second memory 140, and then returns to the normal mode toprocess a corresponding service. However, this is merely an example, andthe CPU 120 may return to the normal mode according to whether the USBis in a first in first out (FIFO) mode or a direct memory access (DMA)mode and may store the data in the first memory 130.

More specifically, if there is the interrupt from the data endpoint,that is, if there is a specific job command, the data of the secondmemory 140 is stored in the first memory 130 which is accessible to theUSB driver in the normal mode. In this case, all hardware is normalizedand the USB driver is driven to process the interrupt and subsequentevents.

That is, the image forming apparatus 100 according to an exemplaryembodiment is configured to process only the service from the controlendpoint in the normal mode. This is due to a limited capacity of thesecond memory 140 which may be realized as an SRAM, an SDAM, and a ROM.

Also, the USB interface 110, the CPU 120, the second memory 140, thefunction unit 150, and the PLL unit (not shown) described above may beintegrated into a single chip such as an application-specific integratedcircuit (ASIC). Accordingly, the image forming apparatus 100 can realizea SoC.

Also, the image forming apparatus 100 may include the engine unit (notshown) to perform an image forming job such as printing, scanning, andcopying in communication with the ASIC unit.

FIG. 1B is a block diagram illustrating an image forming apparatusaccording to another exemplary embodiment.

Referring to FIG. 1B, the CPU 120′ may include a first CPU 121 forsupporting a normal mode and a second CPU 122 for supporting a powersaving mode according to a situation.

The first CPU 121 performs an operation using the first memory 130 inthe normal mode and is deactivated when the normal mode is convertedinto the power saving mode.

The second CPU 122 performs an operation using the second memory 140 inthe power saving mode. More specifically, if a USB data signal is inputin the power saving mode, the second CPU 122 activates the first CPU 121to convert the power saving mode into the normal mode, and if a USBcontrol signal is input in the power saving mode, the second CPU 11retains the power saving mode and performs an operation corresponding tothe USB control signal using the second memory 140.

Also, in the power saving mode, the second CPU 122 may interrupt thepower supplied to the first CPU 121, may lower the operation frequencyof the first memory 130, or may control the first memory 130 to be in aself-refresh mode.

That is, the CPU 120 shown in FIG. 1A is realized by a main controllerthat supports both the normal mode and the power saving mode, whereasthe CPU 120′ shown in FIG. 1B is realized by including a main controllerfor supporting the normal mode and a sub-controller for supporting thepower saving mode, separately.

If the CPU 120 is a main controller for supporting both the normal modeand the power saving mode as shown in FIG. 1A, that is, if a mainfirmware involved in the control of the normal mode and a micro firmwareinvolved in the control of the power saving mode are integrated into asingle chip, the power saving mode is realized by lowering the frequencyof the main controller or by configuring a gated clock in designing themain controller in order to prevent a clock from being input into idleblocks in a standby mode. In this case, the micro firmware may bemounted in an internal memory (SRAM) of the main controller. Since theSRAM maintain its contents without refresh (for example, withoutrecharging), the SRAM has a faster response speed than the DRAM and thusthe power saving mode is converted into the normal mode rapidly.

On the other hand, if the main controller for supporting the normal modeand the sub-controller for supporting the power saving mode are providedseparately as shown in FIG. 1B, that is, if the main firmware involvedin the control of the normal mode and the micro firmware involved in thecontrol of the power saving mode are separate chips, the power suppliedto the elements other than the sub-controller is interrupted in thepower saving mode. In this case, the sub-controller checks whether thereis an interrupt from the USB interface in the power saving mode or not,and, if there is an interrupt caused by USB control communication, thesub-controller processes an event corresponding to the outstandinginterrupt. If there is an interrupt caused by USB data communication,the main controller is activated.

According to another exemplary embodiment, a SoC unit which may bemounted in an apparatus including a volatile memory, may include an USBinterface which receives an USB control signal or an USB data signalfrom an external apparatus connected to the apparatus, and a CPU whichperforms an operation using the volatile memory in the normal mode andperforms an operation using a memory in the power saving mode. If theUSB data signal is input in the power saving mode, the CPU converts thepower saving mode into the normal mode, and, if the USB control signalis input in the power saving mode, the CPU retains the power saving modeand performs an operation corresponding to the USB control signal usingthe memory.

Hereinafter, only the case where the CPU 120 is a main controller forsupporting both the normal mode and the power saving mode, i.e., thecase where the main firmware involved in the control of the normal modeand the micro firmware involved in the control of the power saving modeare integrated into a single chip will be explained. However, it shouldbe understood that diverse exemplary embodiments may be applied if theCPU 120′ includes the main controller for supporting the normal mode andthe sub-controller for supporting the power saving mode as shown in FIG.1B.

FIGS. 2A to 2C are views illustrating diverse examples of the imageforming apparatus as shown in FIG. 1A.

In FIGS. 2A to 2C, only the USB interface 110, the CPU 120, the firstmemory 130, and the second memory 149 of FIG. 1A are illustrated for thesake of simplicity.

As shown in FIG. 2A, the USB interface 110, the CPU 120, and the secondmemory 140 may be provided within a single SoC, and the first memory 130may be provided outside the SoC. In this case, the second memory 140 maybe an SRAM that is reused as a buffer in processing an image or may be aseparate SRAM other than the SRAM that is reused as a buffer inprocessing an image.

Also, as shown in FIG. 2B, the USB interface 110 and the CPU 120 may beprovided within a single SoC, and the first memory 130 and the secondmemory 140 may be provided outside the SoC.

Also, as shown in FIG. 2C, the CPU 120 and the second memory 140 may beprovided within a single SoC, and the USB interface 110 and the firstmemory 140 may be provided outside the SoC. In this case, the USBinterface 110 outside the SoC may be realized using a printer commandlanguage (PCL) inside the SoC.

FIG. 3A is a block diagram to explain a relationship between the imageforming apparatus of FIG. 1A and a host apparatus. Among the elementsshown in FIG. 3A, the same element as those of FIG. 1A and FIGS. 2A to2C are not explained in detail.

A host apparatus 200 may be realized as a personal computer (PC). Insome situation, the host apparatus 200 may be a personal digitalassistant (PDA), a portable multiplayer (PMP), a TV, a server, or etc.

The host apparatus 200 includes an application 210 and a host controller220.

The application 210 may be software for supporting a USB function in anoperation system (OS).

The host controller 220 is a USB bus interface of the host apparatus200, and includes all software or hardware to enable a USB device (thatis, the image forming apparatus 100) to be connected to the hostapparatus 200.

Furthermore, the host apparatus 200 may include a printer driver (notshown) for converting printing data written by an application into aprinter language readable by the image forming apparatus 100. Theprinter driver may be included in the host controller 220. Also, thehost apparatus 200 may include general elements such as an input unit(not shown) and a display unit (not shown).

Hereinafter, general concepts of an endpoint and a pipe will beexplained briefly for easy understanding of the present disclosure.

The endpoint is a logical port and a terminal end in a communicationflow, and has a unique ID. The endpoint has information about adirection of data transmission (an input endpoint and an outputendpoint). The endpoint may describe information such as an accessfrequency of a bus/requirements when the bus is delayed, requirementsfor bandwidth, the number of endpoints, requirements for error handling,a maximum size of packet that is acceptable to the endpoint, atransmission type, and a transmission direction.

The pipe is a connection ring between the endpoint of a single deviceand software of a host. The pipe is divided into a stream pipe and amessage pipe according to its characteristic. The stream pipe and themessage pipe are different from each other and are mutually exclusive.The stream pipe has no USB format defined and supports a one-waycommunication, whereas the message pipe has a defined USB format andsupports a one-way communication.

The endpoint and the pipe are described in detail in the USBspecification and thus a further detailed description is omitted.

The image forming apparatus 100 communicates with the host apparatus 200through a USB, and the USB interface 110 may include a control endpoint111 which is a logical port, and a plurality of data endpoints 112, 113which are also logical ports. The endpoints other than the controlendpoint 111 are slightly different according to how to transmit data,but may be regarded as a simple logical port for transmitting data.Therefore, hereinafter, the endpoint is called “data endpoint”.

The control endpoint 111 is a logical port that determines whether theimage forming apparatus 100 is connected to the host apparatus 200 ornot through a series of enumerations, and that obtains information ofthe image forming apparatus 100 if the image forming apparatus 100 isconnected or sets the image forming apparatus 100 to communicate withthe host apparatus 200. That is, the control endpoint 111 is always usedwhen the enumeration is performed and the device on the bus is operated(when a device is recognized). That is, the control endpoint should be afundamental endpoint for connecting/disconnecting/recognizing a deviceand should be carried by any device, and also, should be controllable.

The control endpoint 111 uses the message pipe unlike the data endpointso that the control endpoint 111 can perform a two-way communication.

The data endpoints 112, 113 are designed to transmit data and may be atleast one type of a bulk type in/out endpoint, an isochronous typein/out endpoint, and an interrupt type in/out endpoint.

The bulk type in/out endpoint is for transmitting bulky data accuratelyat any time, and retransmits the data if there is a transmission errorin the bus. For example, the bulk type in/out endpoint may be used totransmit data of a storage device such as a hard disk. Also, the bulktype in/out endpoint uses the stream pipe and thus has a singledirection.

The isochronous type in/out endpoint is mainly used in a device thatregards a real-time property of an audio as important and likewise usesthe stream pipe and thus has a single direction.

The interrupt type in/out endpoint is mainly used in a device thatrequires periodic signal transmission and reception such as a hub andlikewise uses the stream pipe and thus has a single direction.

Since the image forming apparatus 100 requires transmission of bulkydata, the bulk type in/out endpoint may be used.

Also, the number of the data endpoints 112, 113 and the directions ofthem may be selected according to the interface characteristic. Also,the number and function of the data endpoints 112, 113 are selectivelydetermined by the manufacturer of the apparatus according to thespecification of the apparatus.

For example, in the case of a MFP, the endpoint is configured as shownin FIG. 3B. The endpoint is a logical port rather than a physical portbut is schematized in the drawing for the convenience of explanation.

Referring to FIG. 3B, if an endpoint I 112 is dedicated for a printerand an endpoint II 113 is dedicated for a scanner, an OUT endpoint112′-2 of the endpoint I 112′ is an end point for receiving printingdata from a host apparatus 200′, and an IN endpoint 113′-1 of theendpoint II 113′ is an endpoint for transmitting scanned data to thehost apparatus 200′.

The CPU 120 controls the overall operation of the normal mode in whichthe original function of the image forming apparatus 100 such ascopying, scanning, and faxing is performed.

Also, the CPU 120 is set to be converted from the normal mode into thepower saving mode if a predetermined condition is satisfied. Forexample, if no job command is input for a predetermined time, the normalmode is converted into the power saving mode. However, this is merely anexample. If a specific user command is input, the normal mode may beconverted into the power saving mode.

That is, if the image forming apparatus 100 does not perform any job orif there is no job command to copy, scan, or fax, which may be inputthrough a panel of the image forming apparatus 100, an USB, or diverseuser interfaces such as a network, for a predetermined time, the CPU 120may convert the normal mode into the power saving mode.

If the normal mode should be converted into the power saving mode, theCPU 120 copies a program for controlling the power saving mode from thefirst memory to an executable area of the second memory 140. The firstmemory 130 is a main memory that stores a program or an applicationnecessary for the overall operation of the image forming apparatus 100,and may be realized as a DRAM, and the second memory 140 may be realizedas at least one of an SRAM, an SDRAM, and a ROM as described above.

The program for controlling the power saving mode includes a USB driver,and the USB driver may include only a routine responsible for a processof the control endpoint and a routine required in a wake-up process forreturning to the normal mode. Accordingly, since a low power USB programstored in the second memory 140 has less capacity than a USB programstored in the first memory 130, the second memory 140 may be realized asa small capacity memory.

If the program has been completely copied, power supplied to the entiresystem modules including the first memory 130 is interrupted and theimage forming apparatus 100 enters the power saving mode.

In the power saving mode, the CPU 120 checks whether there is aninterrupt from the control endpoint 111 or the data endpoint 112.

If there is an interrupt from the control endpoint 111, the CPU 120processes a corresponding event by executing the program or theapplication stored in the second memory 140.

If the interrupt is not from the control endpoint 111, that is, if thereis an interrupt from the data endpoint 112, the CPU 120 reads outprinter data and stores it in the second memory 140, and then returns tothe normal mode to process a corresponding service. However, this ismerely an example, and the normal mode may be restored and the data maybe stored in the first memory 130 according to whether the USB is a FIFOmode or the DMA mode.

More specifically, if there is an interrupt from the data endpoint 112,that is, if there is a specific job command, the data in the secondmemory 140 is stored in the first memory 130 which is accessible to theUSB driver in the normal mode. In this case, all hardware is normalizedand the USB driver is driven to process the outstanding interrupt andsubsequent events.

The elements and their arrangement order shown in FIGS. 1A to 3B aremerely an example and some of them may be deleted and an additionalelement may be added. Also, the order may be changed.

FIG. 4 is a view illustrating a system configuration to explainoperations in the normal mode and the power saving mode according to anexemplary embodiment.

Referring to FIG. 4, if an event occurs in the normal mode, for example,if a print command is input through a USB in the normal mode, a USBdevice controller recognizes the event as an interrupt and a CPU isinformed of the occurrence of the interrupt by an interrupt controller.

Upon receiving the interrupt, the CPU processes the interrupt in a mainfirmware of an external DRAM and is ready to print.

If no print command is input for a predetermined time, the CPU tries toenter the power saving mode. When the CPU enters the power saving mode,the CPU copies a micro firmware from the external DRAM to an executablearea of an internal SRAM, and the micro firmware operates instead of themain firmware. At this time, the power supplied to the external DRAM isinterrupted or enters a self-refresh state. The micro firmware includesthe USB driver, and the USB driver includes only a routine forprocessing the control endpoint and a minimum routine for receiving theprint command. The minimum routine for receiving the print commandconfirms that an interrupt has occurred in the endpoint which hasreceived the print command. That is, in the related art, if the DRAM isinterrupted, no service is available through the USB. However, in thepresent disclosure, a minimum driver is driven in order to retain theconnection with a device in the SRAM. If an interrupt occurs in thisendpoint, a wakeup manager notifies that the normal mode should berestored.

FIG. 5 is a view illustrating a USB packet analysis frame according toan exemplary embodiment.

Referring to FIG. 5, the print driver 220 of the host apparatus 200frequently transmits a manufacturer restriction request or a classrestriction request to the image forming apparatus 100 through a controlendpoint (endpoint 0: ENDP 0). After that, bulk transmission accordingto a print command is performed through the endpoint 1 (See “A”). Thismeans that continuous request may be transmitted through the controlendpoint even in the power saving mode. This manufacturer restrictionrequest is different depending on the manufacturer.

If the image forming apparatus 100 according to an exemplary embodimentreceives the request as shown in FIG. 5, all requests for the controlendpoint from Transfer 48 to 64 are processed by the sub-controller,and, if the print command is received at the end point 1 as in transfer65, a corresponding event is processed by the main controller after thenormal mode has been restored.

FIG. 6 is a flowchart illustrating a driving method of an image formingapparatus according to an exemplary embodiment.

Referring to FIG. 6, a driving method of an image forming apparatuswhich is connected to a host apparatus, includes a first memory, asecond memory, and an USB interface to receive a USB control signal or aUSB data signal from the host apparatus, and operates in a normal modeusing the first memory or in a power saving mode using the second memoryis explained. In this method, if a signal input from the host apparatusis detected in the power saving mode (S610), it is determined whetherthe signal is a USB control signal or not (S620).

If the input signal is the USB control signal (S620: Y), the powersaving mode is retained and an operation corresponding to the USBcontrol signal is performed using the second memory (S630).

If the input signal is not the USB control signal (S620: N), that is, ifthe input signal is a USB data signal, the power saving mode isconverted into the normal mode and the first memory is activated (S640).

An operation corresponding to the USB data signal is performed using theactivated first memory (S650).

The USB data signal may be a request signal for an image forming job.

Also, the second memory may be used along with the first memory in thenormal mode.

Also, if the normal mode is converted into the power saving mode, aprogram stored in the first memory for controlling the power saving modeis copied to the second memory, and an operation frequency of the firstmemory may be lowered or the first memory is retained in a self-refreshstate.

The program for controlling the power saving mode may include at leastone of a program for determining whether the USB control signal or theUSB data signal is input, a program for executing the operationcorresponding to the USB control signal, and a program for convertinginto the normal mode according to a type of input USB signal.

The USB control signal may be input through the control endpoint, andthe USB data signal may be input through the bulk type in/out endpoint.The endpoint has been described above and thus a detailed description isomitted.

FIG. 7 is a flowchart illustrating a driving method of an image formingapparatus according to another exemplary embodiment.

Referring to FIG. 7, a driving method of an image forming apparatuswhich is connected to a host apparatus, and includes a first memory, afirst CPU which operates using the first memory in the normal mode andis inactivated if the normal mode is converted into a power saving mode,and a second CPU which operates using a second memory in the powersaving mode is explained. In this method, if a signal input from thehost apparatus in the power saving mode is detected (S710), it isdetermined whether the input signal is a USB control signal or not(S720).

If the signal input from the host apparatus is the USB control signal(S720: Y), the power saving mode is retained and an operationcorresponding to the USB control signal is performed using the secondmemory (S730).

If the signal input from the host apparatus is not the USB controlsignal (S720: N), that is, if the signal input from the host apparatusis a USB data signal, the first CPU is activated and the power savingmode is converted into the normal mode (S740).

The USB data signal may be a request signal for an image forming job.

Also, the second memory may be used along with the first memory in thenormal mode. For example, the second memory may be realized as an SRAMused to perform an image forming job.

If the normal mode is converted into the power saving mode, a programstored in the first memory for controlling the power saving mode iscopied to the second memory and power supplied to the first CPU isinterrupted.

The program for controlling the power saving mode may include a routinefor determining whether a signal is input to a USB interface or not, aroutine for performing an operation corresponding to the USB controlsignal, and a routine required in a wake up process for converting intothe normal mode.

Also, the USB control signal may be input through the control endpointand the USB data signal may be input through the bulk type in/outendpoint. The endpoint has been described above and thus a detaileddescription is omitted.

According to another exemplary embodiment, a driving method of a SoCunit, which is mountable on an apparatus having a volatile memoryaccessible in a normal mode, and includes a USB interface to receive aUSB control signal or a USB data signal from an external apparatusconnected to the apparatus, and a memory, includes: detecting a signalinput from the apparatus in a power saving mode, converting the powersaving mode into a normal mode if the input signal is a USB data signal,and, if the input signal is a USB control signal, retaining the powersaving mode and performing an operation corresponding to the USB controlsignal using the memory in the SoC unit.

The USB control communication may be performed through the controlendpoint, and the USB data communication may be performed through thebulk type in/out endpoint.

The second memory may be realized as at least one of an SRAM, SDRAM, andROM.

The USB interface, a second memory, and a CPU for controlling the normalmode and the power saving mode may be included in the SoC unit.

Also, the present disclosure may include a computer readable recordingmedium which includes a program for executing the above-describeddriving method of the image forming apparatus. The computer readablerecording medium includes any type of recording apparatuses on whichdata readable by a computer system is recorded. The examples of thecomputer recordable recording medium are a ROM, a RAM, a CD-ROM, amagnetic tape, a floppy disk, and an optical data storage device. Thecomputer readable recording medium is distributed in the computer systemconnected over a network and thus a code readable by the computer isstored and executed in a distributed manner.

Although only the USB communication has been described above, thepresent disclosures may be applied to diverse communication schemessimilar to the USB communication scheme, such as network communication,Bluetooth, high definition multimedia interface (HDMI), peripheralcomponent interconnect (PCI) express, Ethernet, ZigBee, FireWire, CAN,IEEE1394, PS/2, accelerated graphics port (AGP), industry standardarchitecture (ISA), micro channel architecture (MCA), extended industrystandard architecture (EISA), video electronics standard architecture(VESA), and etc.

That is, the present disclosure provides a method in which the powersaving mode is converted into the normal mode if an image forming job isreceived through a printing job reception port in the networkcommunication.

As described above, normal USB communication is possible even if thepower supplied to the main memory in which the USB driver is driven isinterrupted. By reusing a small SRAM in the SoC, an increased cost dueto an additional SRAM is solved and the power saving mode is achievedefficiently.

In the above exemplary embodiments, the image forming apparatus has beendescribed, but this is merely an example, and any apparatus that is USBcommunicable can be applied.

Although a few embodiments have been shown and described, it would beappreciated by those skilled in the art that changes may be made in thisembodiment without departing from the principles and spirit of theinvention, the scope of which is defined in the claims and theirequivalents.

What is claimed is:
 1. An image forming apparatus which is connected toa host apparatus, comprising: a first memory; a second memory; auniversal serial bus (USB) interface to receive a USB control signal ora USB data signal from the host apparatus; and a central processing unit(CPU) operating in a normal mode using the first memory or in a powersaving mode using the second memory, wherein, if the USB data signal isinput in the power saving mode, the CPU activates the first memory andconverts the power saving mode into the normal mode, and, if the USBcontrol signal is input in the power saving mode, the CPU retains thepower saving mode and performs an operation corresponding to the USBcontrol signal using the second memory, and wherein the USB controlsignal is input through a control endpoint, and the USB data signal isinput through a bulk type in/out endpoint.
 2. The image formingapparatus as claimed in claim 1, wherein the USB data signal is arequest signal for an image forming job.
 3. The image forming apparatusas claimed in claim 1, wherein the CPU interrupts power supplied to thefirst memory or retains the first memory in a self-refresh state in thepower saving mode.
 4. The image forming apparatus as claimed in claim 1,wherein the second memory and the CPU are provided inside a system onchip (SoC), and the USB interface is provided inside or outside the SoC.5. The image forming apparatus as claimed in claim 1, wherein, if theimage forming apparatus enters the power saving mode, the CPU copies aprogram for controlling the power saving mode from the first memory tothe second memory.
 6. The image forming apparatus as claimed in claim 5,wherein the program for controlling the power saving mode comprises atleast one of a routine for determining whether a signal is input to theUSB interface or not, a routine for performing an operation according tothe USB control signal, and a routine required in a wake up process forconverting the power saving mode into the normal mode.
 7. A drivingmethod of an image forming apparatus which is connected to a hostapparatus, the image forming apparatus comprising a first memory, asecond memory, and a USB interface to receive a USB control signal or aUSB data signal from the host apparatus, and the image forming apparatusoperating in a normal mode using the first memory or in a power savingmode using the second memory, the driving method comprising: detecting asignal that is input from the host apparatus in the power saving mode;and if the input signal is the USB control signal, retaining the powersaving mode and performing an operation corresponding to the USB controlsignal using the second memory, and if the input signal is the USB datasignal, converting the power saving mode into the normal mode toactivate the first memory and performing an operation corresponding tothe USB data signal using the activated first memory, wherein the USBcontrol signal is input through a control end point and the USB datasignal is input through a bulk type in/out endpoint.
 8. The drivingmethod as claimed in claim 7, wherein the USB data signal is a requestsignal for an image forming job.
 9. The driving method as claimed inclaim 7, wherein, in the power saving mode, power supplied to the firstmemory is interrupted or the first memory is retained in a self-refreshstate.
 10. The driving method as claimed in claim 7, further comprising,if the image forming apparatus enters the power saving mode, copying aprogram stored in the first memory for controlling the power saving modeto the second memory.
 11. The driving method as claimed in claim 10,wherein the program for controlling the power saving mode comprises atleast one of a routine for determining whether a signal is input to theUSB interface or not, a routine for performing an operationcorresponding to the USB control signal, and a routine required in awake-up process for converting the power saving mode into the normalmode.